This invention relates in general to an electrical circuit which is capable of isolating particular components while supplying power to a particular device and, more particularly, to an electrical circuit whereby supporting devices in the circuit may be shut down, while power continues to be supplied to a circuit controller without maintaining the surrounding support devices thereby reducing current consumption to near zero.
In the design of electrical circuits, it is customary that the positive supply is opened when it is desired to interrupt or terminate power to the circuit or components thereof. However, when it is desired to supply power to a particular component of a circuit, the particular circuit component can be maintained in an operable condition without maintaining surrounding support devices by shutting down the return mode, not the supply mode of the system, by opening the system ground return rather than interrupting the positive supply. In this manner, the current consumption can be limited to that required for maintaining the particular circuit component active, and has many practical applications wherein it is desired to conserve a power supply such as a battery.
Interrupting the power supply to a circuit by opening the system ground return rather than the positive supply is known to those skilled in the art, and has been used in circuits for such things as power line load control, U.S. Pat. No.3,448,361, and in a timing controller, in U.S. Pat. No. 4,672,232. In U.S. Pat. No. 3,448,361, "SELECTIVE-FREQUENCY POWER LINE LOAD CONTROL", a semi-conductor controlled rectifier (SCR) is coupled between an individual load coupled to a power line, and ground. In operation an individual load is coupled in series with the SCR across the power lines, and when the control electrode of the SCR is triggered "on" by a control voltage, current flows through the load. Current flow is interrupted when the control electrode is not triggered, thereby interrupting power to the load on the system ground return. In U.S. Pat. No. 4,672,232, "MICROPROCESSOR OPERATED TIMING CONTROLLER", an electronic switching device is coupled between an individual load, an appliance receiving receptacle, and ground. In operation the electronic switch is controlled by a microprocessor, which closes the switch to complete a circuit for energizing the receptacle. In the absence of a control signal from the microprocessor, the electronic switch opens the return path to ground, and the appliance plugged into the receptacle is turned off.
In the instant circuit, a single switch is utilized within a common ground line to control the current flow through a plurality of loads, whereby power to all of these loads may be interrupted by opening the system ground return so that power can be supplied to a particular component of the circuit, a microprocessor, to the exclusion of all remaining components by the operation of a single switch.